1. Field of the Invention
The invention relates to the field of aircraft restraining systems and, in particular, to a cable restraint system for an aircraft for use during engine run up tests.
2. Description of Related Art
After repair or replacement of an engine in an aircraft, it is necessary to check out engine performance on the ground prior to any flight test. During these tests, it is often required that the engines be run at or near full power and it is therefore necessary to physically restrain the aircraft. On early aircraft designs having non-retractable landing gear wherein the wheels are connected by a common shaft, restraint systems as disclosed in French Patent No. 617,573 by. M. Dauvin could be used. The aircraft is restrained by a vertical "Y" shaped member having the center member or leg of the Y either driven into the ground or encased in concrete. The "harms" of the Y are pivotally connected to the common landing gear shaft in proximity to the wheels, and to the center member. Additionally, three cables are attached by one of their ends to the center member and extend radially outward therefrom, having their second ends attached to pins inserted into the ground. While such a system will work, it is totally unusable with aircraft using retractable tricycle landing gear, thus eliminating its use on virtually all modern aircraft.
Of course, wheel chocks cannot be seriously considered for use during part or full power engine run-up tests because of the danger that they may move or that the wheels will ride-up and over them, especially if they are not properly positioned. Separate cables attached to each main landing gear, as disclosed in U.S. Pat. No. 2,469,659 "Tethering Device For Airplanes" by J. Martin, have been used, but the storage and tracking of separate cables is a drawback. In addition, on aircraft such as the F-117 Night Hawk aircraft, running two separate cables directly back to a ground attachment fitting at an acute angle can cause interference with the landing gear doors. The use of such cables or chains to hold the aircraft to the deck of an aircraft carrier is discussed in U.S. Pat. No. 3,904,154 "Securing System For Jet Engine Testing Of Aircraft" by F. W. Jones. Additionally, attempts to use tie-down rings on the main landing gear can also cause problems. For example, on the F-117 aircraft with tie-down rings off-set from the centerline of the gear, the cables when loaded during engine run-up can cause damage to the landing gear torque arms.
Thus, it is a primary object of the invention to provide an aircraft restraint system for engine run-up tests.
It is another primary object of the invention to provide an aircraft restraint system for engine run-up tests that is easy to attach to the aircraft.
It is a further object of the invention to provide an aircraft restraint system for engine run-up tests that is easy to store.
It is a still further object of the invention to provide an aircraft restraint for engine run-up tests that allows self alignment of the aircraft.
It is another object of the invention to provide an aircraft restraint system for engine run-up tests that includes tie down redundancy.